Similar to much of the existing work in the field [1]}, the communication in our experiments is asymmetrical (i.e. the action space of the speaker and listener are different). During unsituated communication, we simulate a passive listener that can take environmental actions and receive signals from a speaker but cannot send signals itself. If the agents' action spaces were symmetrical (the scenario considered by Wagner et al., 2003), this would be a somewhat degenerate case—communication would never emerge between two agents who can only receive signals and take environmental actions. As a result, our definition of unsituated communication deviates slightly from the definition introduced by Wagner et al. (2003).
